Multi-leaf collimators are comprised of a plurality of individual parts (known as “leaves”) that are formed of a high atomic numbered material (such as tungsten) that can move independently in and out of the path of the radiation-therapy beam in order to selectively block (and hence shape) the beam. Typically the leaves of a multi-leaf collimator are organized in pairs that are aligned collinearly with respect to one another and that can selectively move towards and away from one another via controlled motors. A typical multi-leaf collimator has many such pairs of leaves, often upwards of twenty, fifty, or even one hundred such pairs.
By passing a therapeutic radiation beam through the aperture(s) of a multi-leaf collimator the radiation beam can be modulated to better match the dosing requirements of the treatment session. These dosing requirements typically include (or at least presume) prescribing which body tissues to irradiate and which body tissues to avoid irradiating.
While a typical multi-leaf collimator represents an enormous improvement in terms of better shaping a radiation beam to meet such requirements, it nevertheless remains true that, at least some of the time, the resultant beam shape does not perfectly meet such requirements. This shortcoming typically arises as a function of the maximum resolution by which the multi-leaf collimator is able to shape the beam. When the leaves of the multi-leaf collimator have a cross-dimension of, for example, 1.0 centimeter, that is generally orthogonal to the incoming beam, that dimension imposes a corresponding limit as to the resolution capabilities of the collimator.
Elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions and/or relative positioning of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present teachings. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present teachings. Certain actions and/or steps may be described or depicted in a particular order of occurrence while those skilled in the art will understand that such specificity with respect to sequence is not actually required. The terms and expressions used herein have the ordinary technical meaning as is accorded to such terms and expressions by persons skilled in the technical field as set forth above except where different specific meanings have otherwise been set forth herein.